Renewable enclosed fuse



June 5, 1951 F. G. voN HooRN RENx-:wABLE ENCLOSED FUSE Filed Feb. 19, 1946 Inventor:

Fred 'GX/on Hoorn,

m l-| i s Att ovm ey.

outer .face thereof and flattened edges I3.

Patented June 5, 1.951

vRENEW/ABLE ENCLOSED FUSE vFred G. von Hoorn, Bridgeport, Conn., assigner to General Electric Company, a corporation of `New York Application February 19, 1946, Serial No. 648,764

9 Claims. 1

My invention relates to electric fuses and more particularly to a `fuse of ythe enclosed type yin -which'provision is made for renewal of the fuse link.

vOne'object of my invention is to provide a new and improved fuse construction incorporatvingmeans to secure a magnetic blowout of the :fusearc when the link ruptures.

delay inl'blowing of the fuse link and in which av magnetic ux is utilized to extinguish the are when the link blows after a predetermined time delay.jf`.

Still another object of my invention is to pro- -vide an lenclosed fuse so constructed as to permit quick and easy renewal of the fuse link.

A'further object is to provide an enclosed fuse vin which the parts are so arranged as to permit easy assembly during manufacture and which when assembled forms a rugged construc- :tion well suited for frequent renewal of the fuse link without damage to the parts.

In vthe accompanying drawing, Fig. 1 is a sectional view through a fuse constructed in accordance with my invention; Fig. 2 is a view showing the parts removed from the casing; Fig. 3 is a perspective view showing the arrangement of parts at one end of the fuse; Fig. 4 is a view; showing certain of the parts in -posi- -tio'n for assembly; Fig. 5 is a sectional view of a modied construction, and Fig. 6 is a view of the-modication taken along the line 6-6 of lReferring to the drawing, the fuse I is provided ,with spaced knife-blade terminals 2 and 3 interconnected by a rigid bar 4 of insulating material, such as impregnated sheet fiber or asbestos, A fuse link 5 extends betweenthe terminals. The assembly is housed within a tubularcasing 6 formed of any suitable insulating material such as a plastic impregnated ber. `(lne end of the casing `is provided with a ferrule I having anvcpening 8 vfor accommodating the terminal 3. The other end of the casing is screw threaded, as 'indicated by numeral 9, for receiving a cap I0. By unscrewing the cap I 0, the fuse lmechanism may be removed as a -unit `from the `casing to permit renewal of the fuselirik 'iIn order Yproperly `to support the fuse mechanism within Vthecasing, the :terminal 3 is provided vwith :a washer II staked thereon, the 'washer being provided with scorings I2 on the As .will Aappear presently, the .washer is so formed -to :provide for venting of the fuse casing. Similarly. the other terminal 12 is provided with a :washer IIIl :having afscoredsurface I5, the washer being staked :to lthe terminal. Inf-addition, the

terminal r2 carries a cover plate I6 immediately adjacent the washer I4 and which cooperates with the cap I!) to form a closure for that end of the fuse. The washer I4 is provided with diametrically opposite projections I'I which rest in notches I8 in the end of casing 6 when the fuse mechanism is mounted in position. When the projections Il nest in the notches I8, there is no danger of twisting the terminal 2 within the casing upon tightening down on cap III. In order to prevent the cap III from falling oil' the terminal 2 during disassembly of the fuse, the terminal is provided with two punched ears i9 against which the cap rests.

In assembling the fuse mechanism withinthe casing, the terminal 3 is inserted through the opening il in ferrule 'I so that the washer II rests against the inner face of the ferrule. In this position of the fuse mechanism, the projections I'I rest in the notches I8 on the end or" the fuse casing, with the washer I4 nested within the casing and the closure plate I6 resting on the threaded end of the casing. This position of the parts is shown by Fig. 1. The cap Iii is now threaded down on the casing to hold the mechanism firmly in position.

Proper venting of the fuse is secured at each end of the casing. At one end, the flattened edge I3 of the washer II and the scorings I2 form a passageway 2G for the hot gases generated upon blowing of the fuse link. The gases ow through the passageway and out through the opening 8 in the ferrule. The terminal 3 has a suiciently loose fit in the ferrule I to permit this. At the other end, the gases vent around the edges of the washer I4 and then pass through a clearance channel formed by the threads on cap III and casing 6. The channel is formed by cutting off the `tips of the threads, as is common practice in the fuse art. Gases also ow through the passageway formed by the scorings I5 and then out between the closure plate IS and blade 2 .through an opening similar to that provided at 8. The cap I0 is threaded down tightly by hand to hold the parts in assembled position, but due to manufacturing tolerances in the parts sufficiently small openings are formed to permit proper venting in the manner indi cated. I

The fuse'mechanism thus far described may be easily and quickly removed from the casing simply by unthreading the cap I6. It comes out of the casing in a single piece so that there is no danger of any parts being When removed from the casing, the blown fuse link may be easily replaced with a new one. Another advantage is that the end of the casing is then absolutely clear -of` parts so that fragn ments of the blown fuse may be readily removed from the casing. i

One important feature of my invention is the manner in which the" terminals and insulating rod are assembled together. Referring to Figs. 3 and 4, it will be seen that the inner part oi the terminal 2 comprises a flat strip of material 2|, such as heavy sheet copper, and which is formed with projecting ribs 22 on its opposite sides. The ribs 22 form a guideway for a U-shaped slip 23. The arms of the U are formed with grooves 24 into which the ribs project to hold the parts together, the arms thereby embracing and clasping the edges of terminal 2. A clamp 25 overlies the terminal and is used to secure the fuse link in position. A screw 26 extends through opening 21 formed in the clamp and is threaded into tapped opening 28 in the terminal 2. It passes through a slightly undersized opening 23 in the insulating rod 4 and extends through a clearance hole 3!) in the clip 23.

In assembling the insulating bar on the terminal, the clip 23 is held in a iixture and bar 4 placed inside the clip. The blade 2| is then slipped into position with the ribs 22 seated in grooves 24. The fuse link and clamp 25 are then assembled on blade 2 l. Screw 26 is threaded through the parts to hold them in assembled relationship. The construction is one which is easily and quickly assembled. It requires only a single fastening screw. In order to prevent loosening of the screw, the hole 29 in the liber bar is punched slightly smaller than the outside diameter of the screw. This means that when the screw is threaded into position, it cuts 1 `threads in the ber bar which frictionally grip the screw and give a locking action. However, the screw may be easily unthreaded to release clamp when replacing the fuse link. When renewing the fuse link, it is not necessary to disassemble the parts because only the clamp 25 need bev lifted slightly to permit insertion of a new link. Since the ber bar 4 is clamped in position by the terminal 2 and clip 23 for a substantial distance along its length, the assembly gives an exceptionally rigid construction. This means that the two terminals are held securely in alignment so that no stress is placed upon the fuse link.

The fuse link 5 is so designed for use in conjunction with the terminals 2 and 3 as to give a time delay action of the fuse. To this end, the link is provided with a slot 3| adjacent each end which forms blow points 32 on opposite side edges of the link. sembled on the terminals, the blow points 32 are located immediately adjacent the end of clamp 25 and are close to the mass of material formed by the strip 2| of the terminal. On substantial overloads -for short periods of time, the heat generated in the blow points 32 will be absorbed and dissipated by the large mass of metal formed by the terminal strip 2|. Since this is formed of copper, it comprises a good hea-t conducting material. The clip 23 and clamp 25 also assist in conducting away the heat. This means that on high overloads of short duration,

a time delay action is secured so that the i'use will not rupture when excessive surges occur' in the line for relatively short periods of time, for example, as when starting a motor.

. In order to facilitate blowing of the link on very heavy cverloads, it is provided with spaced vslow points 33 in addition to the blow points 32. When the fuse is subjected to such @vel-loads, it

When the fuse link is asl f 4 will blow at the point 33. This means that the middle section 34 will drop out forming a large gap in the link to extinguish the arc.

Under certain conditions of light overload for prolonged periods of time, the link will blow in the center section 34. The reason for this is that the heat generated in the link at both blow points 32 and 33 will be absorbed and dissipated along the opposite ends of the links to the heat absorbing masses formed by the terminals 2 and 3. On short circuit, the link will blow at both Vthe blow points 32 and 33.

In order to prevent damage to the terminal strips 2| upon rupture of the link at the blow points 32, the clamp 25 is provided with an arcing tip'35 which extends upwardly away ,from the end face of the terminal strip 2|. Any `arcing between the link and the terminal construc tion takes place between the link and this arcing tip rather than between` the link and the end face of the terminal strip 2 This arrangement prevents pitting and burning of the terminal strip 2|. The arcing tips 35 are formed at both ends of the clamp 25 so that in the event that one of the arcing tips becomes unduly burned or pitted, the clamp may be reversed in position' to utilize the arcing tip at its other end. It should be noted that the insulating bar 4 is formed of fire and arc resistant material such as an im,- pregnated asbestos ber which is capable v of withstanding the high temperatures existing in the arc when the fuse blows.

Another important feature of my invention is the provision of a magnetic blowout construction which aids in extinguishing the arc upon blowing of the fuse link. To this end, the U-shaped clip 23 is made of any suitable magnetizable material, such as sheet steel. As shown in Fig. 3, the side arms of the U are extended along the length of the bar 4 beyond the end of the terminal strip 2| a distance such that they overlie the blow points 32. When high currents low through the terminal construction, including the clip 23, upon rupture of the blow points 32, a magnetic flux is set up between the arms of the U-shaped clip 23. This flux crosses the path of they arc and has a tendency to draw it toward theber insulating bar 4 to break the arc and extinguish it. This increases the speed with which the arc is interrupted. Moreover, the action of the magnetic blowout helps to prevent damage to the end face of the terminal strip 2|. In this way, the magnetic iiux helps protect the terminal the same as the arcing tip 35. i

After the fuse blows, the link may be easily replaced by unthreading the cap I3 and removing the knifeblade terminals and insulating bar. A single turn on the screws 26 will loosen the clamps 25 sufficiently to permit removal of the link fragments and insertion of a new link.' The link is provided with slotted ends of agconventional form to permit easy insertion of the link and to position the link properly on the terminals.

Figs. 5 and 6 illustrate a modication 4of .the construction in which a blade spring .36 is. inserted between the insulating bar 4 and the `terminal blade 2|. The spring is'provided'with an opening, not shown, for receiving the screw 26. It acts as a spacer to provide wider'separation of the bar 4 and the fuse link so that when the fuse link expands on heating, it does not engage the bar and alter calibration of the fuse. Inaddition, the spring" 36 is sufficiently strong to. keep the assembly snug and tight without requiring close manufacturing tolerances of the parts.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric fuse, spaced knife blade terminal strips, U-shaped clips carried by said strips, the arms of the U and side walls of the strips being provided with cooperating groove and ridge means whereby said clips may be slidably mounted in position on said strips to form a space between the strips and clips, an elongated bar of insulating material having its ends resting in the said spaces to support the terminal strips on the bar, a fuse link extending between said terminal strips, clamps overlying the ends of the links, and separate screw means extending through the clamps, clips and terminal strips to fasten these parts in position on the insulating bar.

2. An electric fuse comprising, in combination, an elongated bar of insulating material, spaced apart knife blade terminal strips connected to opposite ends of the bar, a fuse link connected between the terminal strips, said link being provided with blow points located adjacent the ends of the terminal strips, and a metallic U-shaped member located at each terminal strip, the arms of the U extending near a corresponding blow point to generate a magnetic ilux to extinguish the arcs at the blow points upon rupture of the fuse.

3. An electric fuse comprising, in combination, spaced knife blade terminal strips, a metallic U-shaped clip carried by each of said strips, an elongated bar of insulating material having its ends clamped between the U-shaped clips and the terminal strips, a fuse link connected between the terminal strips, said link being provided with blow points located adjacent the ends of the terminal strips, the arms of the U-shaped clips extending beyond the ends of the terminal strips to points near a corresponding blow point so that upon rupture of the fuse, a magnetic flux is generated between the clip arms to extinguish the arcs at the blow points, and a casing enclosing the fuse link and parts of the terminal strips.

4. An electric fuse comprising, in combination,

ran elongated bar of insulating material, spaced apart knife blade terminal strips connected to opposite ends of the bar, a fuse link connected between the terminal strips, a casing enclosing the fuse link and parts of the knife blade terminal strips, said fuse link being provided with blow points located adjacent the ends of the terminal strips, and a clamping member carried by each of said terminal strips for securing the fuse link in position, each of said clamping members being provided with an arcing tip extending beyond the end of the corresponding terminal strip to receive the arc formed upon rupture of the fuse at the blow points.

5. An electric fuse comprising, in combination, a bar of insulating material, spaced apart knife blade terminal strips mounted on opposite ends of the bar, U-shaped clip members carried by the terminal strips and extending around the ends of the bar, a fuse link connected between the terminal strips, a clamping member carried by each of said terminal strips for securing the fuse link in position, each of said clamping members being provided with an arcing tip extending beyond the end of the corresponding terminal strip to receive any arc formed upon rupture of the fuse link, screw means fastening the clamps, clips and terminal strips to opposite ends of the insulating bar and a casing enclosing the fuse link, the insulating bar and portions of the knife blade terminal strips.

6. A fuse comprising, in combination, a bar of insulating material, spaced apart knife blade terminal strips mounted on opposite ends of the bar, U-shaped clip members carried by the terminal strips and extending around the ends of the bar, a fuse link connected between the terminal strips, said fuse link being provided with blow points located adjacent the ends of the terminal strips, a clamping member carried by each of said terminal strips for securing the fuse link in position, each of said clamping members being provided with an arcing tip extending beyond the end of the corresponding terminal strip to receive any arc formed upon rupture of the fuse at the blow points, the arms of the U-shaped clip members extending beyond the ends of the terminal strips near the corresponding blow points in the fuse link, thereby to provide a magnetic flux to extinguish the arc at the blow points.

7. A renewable electric fuse comprising, in combination, an elongated bar of insulating material having a pair of opposed faces, a conducting terminal strip member overlying a portion of the bar at each end thereof to be engageable with one of said faces, a U-shaped clip member overlying the opposite face of each of said bar portions to have the clip base substantially parallel thereto while the clip arms extend toward said terminal strip, means comprising a projection on one of said members interlocking said strip and said clip to prevent separation of said member by transverse movement between them without limiting relative longitudinal movement therebetween, a fuse link extending between the terminal strips, and screw means engageable with said terminal strip and extending through registering bores in said bar and said clip for securing said link to said strip and for locking said bar, said strip and said clip against relative longitudinal movement thereby effecting a sturdy assembled relationship.

8. A claim in accordance with claim '7 in which said means interlocking said clip and said strip comprises a projection on each of the arms of said U-shaped clip, a complementary recess on each side of said terminal strip whereby said U- shaped clip and said terminal strip are interlocked to prevent transverse movement in one direction, and a compression spring member interpositioned between said terminal strip and said insulating bar to limit transverse movement of said clip and said bar in the opposite direction.

9. A claim in accordance with claim 7 wherein said U-shaped clip and said terminal strip have complementary projections preventing relative transverse movement in one direction and wherein a resilient compression member is positioned between said terminal strip and said insulating bar to limit relative transverse motion in the other direction.

FRED G. voN HOORN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 526,502 Rau Sept. 25, 1894 1,005,253 Mallory Oct. 10, 1911 1,854,454 Cook Apr. 19, 1932 1,860,313 La Mar May 24, 1932 1,881,351 Bussmann Oct. 4, 1932 2,079,097 Wood May 4, 1937 2,175,436 Kellner Oct. 10 1939 2,280,565 Wood Apr. 21, 1942 

